1. Field of the Invention
The invention relates to an amplifier apparatus and particularly relates to a soft-start mechanism and a soft-start method of the amplifier apparatus.
2. Description of Related Art
In electronic apparatuses, the soft-start mechanism is an important mechanism and is often used. In the initial stage of starting up the electronic apparatus, an output voltage provided by an internal circuit needs to rise slowly from 0 volt to the required voltage value, rather than quickly jump to the required voltage value. Thus, it is required to dispose a mechanism for soft-start in the circuit.
The soft-start mechanism is mainly used to suppress an overshoot that may occur due to the rapidly increasing voltage value of the output voltage in the initial stage of starting up the electronic apparatus. The phenomenon of the excessive voltage value is often accompanied by the generation of an excessive output current. The excessive output voltage and output current may damage or even burn the circuit that receives the output voltage. The excessive output current may also cause electromagnetic interference, which affects functions of the electronic apparatus. In addition, if voltage comparison is made based on the output voltage, damping resulting from the overshoot of the output voltage may cause an erroneous comparison result and affect the overall operation of the electronic apparatus.
According to the conventional technology, a soft-start method for a differential amplifier has been proposed. Basically, the conventional method is to gradually increase the voltage value of the reference voltage that serves as the comparison reference by a digital means. Such a method can control the speed of gradual increase of the output voltage. However, since the output voltage is increased step by step gradually by the digital means, and the overshoot problem of the output voltage cannot be completely eliminated.